Study Of Effective Carrying Capacity Of Water-based Drilling Fluids In Horizontal And Deviated Wells

In the process of ERD operation,cuttings bed frequently occurs,especially in highly deviated and horizontal section,which directly affects the safety,efficiency and economy of oil and gas engineering.The ratio of yield point to plastic viscosity??₀/?_p?,low shear rate viscosity?LSRV?and gel strength of drilling fluid are the most controllable factors affecting the hole cleaning.Nowadays,the condition of rheology modifier is that there are not many type of additives we can choose,still,the effect is not ideal.Therefore,it?s high time to develop a novel rheology modifier with high?₀/?_p,LSRV and temperature resistance,which is also an international hot topic.In order to improve the?₀/?_p and LSRV of drilling fluid in horizontal well,a novel polyacrylamide rheology modifier?SDR?which has a high?₀/?_p and LSRV was developed based on the molecular structure design and optimizing the synthetic conditions.The SDR was characterized via FT-IR,TGA and intrinsic viscosity measurement,which show that the SDR has targeted molecule structure,high thermal stability,and its viscosity average molecular is from 0.6 to 1 million.The performance evaluation shows that SDR has better rheology modify property,LSRV value and temperature resistance than XC.The micro-mechanism is thus discussed:through the bridging and adsorption of the strong hydrophilic group of SDR,a 3D network of“polymer-solid particles-SDR-water”was developed;In addition,hydrophobic association structure between intermolecular and intramolecular was formed in the drilling fluid,due to the embedded distribution of the hydrophobic groups.Thus a complicated 3D network structure with a certain gel strength was established,which show a unique rheological properties.Using the novel rheology modifier?SDR?as key additive,a water-based drilling fluid which has a high carrying capacity and excellent comprehensive performance was optimized.This drilling fluid formula has a high?₀/?_p and LSRV value,and it has an excellent shear thinning behavior,a high gel strength and temperature resistance.Finally,in order to learn the actual regular effect of drilling fluid rheological and inclination angel to the borehole annular cuttings concentration,the experimental analysis of the drilling fluids carrying capacity was studied using the newly self-developed cuttings transport simulating test device,and verify that the optimized ERD drilling fluid can keep hole clearning in 0⁹0°angle range.